Built and social environment characteristics associated with motorcyclist mortality in Latin American cities from the SALURBAL study.

Background: Motorcyclists are the fastest growing road user group in Latin America, and account for 25% of all road traffic collision deaths. This study examines the relationship between motorcyclist mortality and the built and social urban environment in Latin American cities.

Methods: We studied 337 cities with ≥ 100,000 inhabitants in seven Latin American countries. Mortality data from 2010 to 2019 were obtained from civil registries and linked to cities defined by the SALURBAL project. Motorcyclist deaths were identified using ICD-10 codes, with redistribution of ill-defined codes. City-level measures included population, urban development, street design, public transportation, and social environment. Associations were estimated using multilevel negative binomial models. A subanalysis of 300 cities with motorcycle registration data was conducted.

Results: The crude city-level motorcyclist mortality rate was 4.16 per 100,000 population. Age-standardized rates varied from 0.51 to 22.60. Males had higher mortality rates, with the highest rates in 20-24-year-olds. After adjustment, cities with higher population density (RR 0.92 [95% CI 0.85-1.00]), intersection density (RR 0.91 [95% CI 0.83-0.99]), and social environment index (RR 0.88 [95% CI 0.83-0.93]) had lower motorcyclist mortality. More curvilinear street layout (RR 0.97 [95% CI 0.90,1.03]) and the presence of public transportation (RR 0.94 [95% CI 0.87,1.03]) showed a non-significant association with mortality. Higher urban development isolation (RR 1.07 [95% CI 1.00-1.14]) was associated with higher mortality, but the association weakened after adjustment. In cities with motorcycle registration data, higher rates of registered motorcycles were associated with higher motorcyclist mortality.

Conclusion: Motorcyclist road traffic deaths in Latin American cities are associated with specific city-level characteristics. In fully adjusted models, higher intersection density and a stronger social environment index were linked to lower mortality rates. City-level interventions that improve street connectivity, promote safer and more cohesive urban environments, and address social inequities in infrastructure and services may help reduce motorcycle deaths and enhance road safety in the region.